1. Field of the Invention
This invention relates to a process for the preparation of oxytitanium phthalocyanine (abbreviated as "TiOPc" hereinafter). More precisely, it relates to a process for the preparation of crystalline TiOPc using dichlorotitanium phthalocyanine and/or dibromotitanium phthalocyanine as a starting material.
2. Description of the Prior Art
Phthalocyanines have been well known as a useful material for the electronic industry as well as a coloring material for paint, printing ink, resin material and the like, and they are widely used as a material for electrophotographic photoreceptor.
During our investigation of preparation methods of TiOPc, we found TiOPc showing major diffraction peaks at Bragg angles (2.theta..+-.0.2.degree.) of 9.3.degree., 10.6.degree., 13.2.degree., 15.2.degree., 20.8.degree. and 26.3.degree. (designated as "A-type TiOPc" hereinafter), TiOPc showing major diffraction peaks at Bragg angles (2.theta..+-.0.2.degree.) of 7.6.degree., 10.2.degree., 22.3.degree., 25.3.degree. and 28.6.degree. (designated as "B-type TiOPc" hereinafter) and TiOPc showing major diffraction peaks at Bragg angles (2.theta..+-.0.2.degree.) of 7.0.degree., 15.6.degree., 23.4.degree. and 25.6.degree. (designated as "C-type TiOPc" hereinafter) in their X-ray diffraction spectra and proposed the production methods for those TiOPc's (Japanese Patent Application Laying-open Nos. 62-256865, 62-256867 and 63-366).
However, those prior methods require precise adjustments of the parameters such as the temperature elevation rate during the reaction of o-phthalodinitrile and titanium tetrachloride and the filtration temperature after the reaction, and the products of those methods tend to contain two or more TiOPc crystalline forms.
Japanese Patent Application Laying-open No. 61-217050 discloses a method for the preparation of TiOPc wherein dichlorotitanium phthalocyanine (abbreviated as "TiCl.sub.2 Pc" hereinafter) is heated with concentrated aqueous ammonia and washed with acetone to obtain TiOPc. However, the product of this method also tends to contain the both of A-type and B-type crystals of TiOPc, and it requires laborious operation.
Further, this prior method involves further drawbacks because of the use of TiCl.sub.2 Pc as the starting material. That is, TiCl.sub.2 Pc is produced by a condensation reaction, of o-phthalodinitrile and titanium chloride and a hydrolysis of the condensation product with water or aqueous ammonia according to the following scheme; ##STR1## however, the hydrolysis of this process requires a lot of time and the crystallinity of the produced TiOPc is relatively low. Therefore, the prior methods using TiCl.sub.2 Pc such as described above are extremely time-consuming and usually require a further physical or chemical treatment such as a treatment with N-methylpyrrolidone, acetone and the like.
On the other hand, a method for the production of TiOPc showing a specific crystalline form by means of a physical treatment had been also proposed in Japanese Patent Application Laying-open No. 64-17066. This patent document discloses a method for the production of TiOPc showing the most distinct diffraction peak at a Bragg angle (2.theta..+-.0.2.degree.) of 27.3.degree. and other peaks at 9.7.degree. and 24.1.degree. (designated as "D-type TiOPc" hereinafter), wherein TiOPc is ground with polyethylene glycol by means of a sand grinder and then treated with diluted sulfuric acid to cause a crystalline transition. However, this method also requires precise adjustments of the conditions such as the agitating conditions during the grinding, and the product also tend to contain two crystalline forms of TiOPc.
The object of the present invention is, therefore, to provide a novel method capable of eliminating the drawbacks of the prior methods described above and selectively producing TiOPc showing a specific crystalline form of A, B, C or D-type.